Input devices for computers are well known in the art. There are several types of input devices, such as the familiar "mouse", which have been utilized and are generally useful in providing "user friendly" computer systems for both technical and non-technical applications. The popularity which these devices have achieved in the art can be given large credit for fostering the explosive growth of the personal computer industry since they provide a simple means for users to input data to computers for users.
Currently, about 95% of all input devices or "pointing devices" are mice. A mouse generally requires a free-rolling surface on which it can interface. Depending upon the particular mouse which is used, the device couples to the free-rolling surface and translates movement across the surface as an input to a computer. Thus, the mouse is unsuitable for any input application which cannot provide space for a rolling surface. The current and growing popularity of "laptop" computers thus has created a significant problem for mouse type technologies which require a rolling surface. Laptops are generally used in small confined areas such as, for example, airplanes, where there is insufficient room for a rolling surface. Therefore, a long-felt need in the art exists for non-mouse pointing solutions for computers and other instruments.
A further long-felt need in the art exists for input and pointing devices which are simple to use and which can be easily integrated with current computers. This long-felt need has not been solved by previous mechanical ball or shaft rolling technologies, such as, for example, track balls. Furthermore, new pointing devices should be reliable and rugged, with the ability to be transported to a variety of locations. Current track ball devices do not satisfy these long-felt needs and are also quite cumbersome since they require practiced dexterity by the user as he interacts with the device.
Other types of pointing or input devices have been employed in the art. U.S. Pat. No. 3,886,311, Rodgers et al., discloses a writing pen for detecting time varying electrostatic field components. The writing pen disclosed in Rodgers et al. is used in conjunction with a writing tablet which generates an electrostatic field. The Rodgers et al. patent discloses an X-Y grid having a writing surface overlaying the grid and an active stylus which writes on the grid in the same manner as a ball point pen. See column 2, lines 63, through column 3, line 7.
Other examples of stylus-type or "tablet" input devices are disclosed in U.S. Pat. No. 4,672,154, also to Rodgers et al. The second Rodgers et al. patent discloses a cordless stylus which emits a directional electric field from the tip of a conductive pen cartridge. The pen tip is capacitively coupled to a digitizer tablet having an X-Y coordinate system. The pointing device disclosed in the second Rodgers et al. patent may also function as a mouse. See column 1, lines 65 through 68. Both the stylus embodiment and the mouse embodiment disclosed in the second Rodgers et al. patent are both active devices which emit electrostatic fields that interface with the digitizer tablet.
The Rodgers et al. patents disclose digitizing styluses and mouse pointing devices which require a separate rolling surface. Furthermore, both of these patents disclose devices which are active and emit electrostatic fields to interact with the digitizing tablet in order to input data to a computer. Since the devices disclosed in both Rodgers et al. patents are active, the stylus is either attached to the tablet by a wire or contains a replaceable power source such as a battery. In either case, the user is required to grasp a bulky item in order to use the device. Thus, the devices disclosed in the Rodgers et al. patents do not satisfy a long-felt need in the art for pointing and input devices which can be conveniently and efficiently used for a variety of portable and desktop applications.
It has been known in the art to use tactile sensing devices to provide data input. See U.S. Pat. No. 4,680,430, Yoshikawa et al. The Yoshikawa et al. patent discloses a coordinate detecting apparatus for determining the coordinate position data of a point on a plane indicated by the touch of a finger tip or other load. Yoshikawa et al. teaches an analog type apparatus which uses a resistive film through which the coordinate position of a point is detected. The point's coordinate position is indicated by applying a load impedance to the position. See column 3, lines 8 through 22.
Tactile devices such as those disclosed in Yoshikawa et al. exhibit a significant disadvantage since they require electrical contact between the finger tip and the device. When individuals possess long fingernails or have other objects about the fingers and hands, good electrical contact is prevented and the device does not function properly.
Other analog tactile devices also exist in the art. See, e.g., U.S. Pat. No. 4,103,252, Bobick. The Bobick patent discloses electrodes located on the boundaries of a sensing region. Human touch on an edge of an electrode produces a capacitive charge to vary the time constant of an RC network which is part of an oscillator. The variation in capacitance of the sensor changes the time constant of the RC network and results in a change in frequency in the output signal of the oscillator. See column 2, lines 8-20.
U.S. Pat. No. 4,736,191, Matzke, discloses a touch activated control device comprising individual conductive plates which form sectors of a circle. A user's touch on the dielectric layer overlaying the plates is detected by individually charging and discharging each of the sectors in the plates in a sequential manner to determine the increased capacitance of the sector. See column 2, lines 26 through 40.
Display devices which are touch sensitive have also been utilized in the art. See U.S. Pat. No. 4,476,463, Ng et al. The Ng et al. patent discloses a display device which locates a touch anywhere on a conductive display faceplate by measuring plural electrical impedances of the faceplate's conductive coating. The impedances are at electrodes located on different edges of the faceplate. See column 2, lines 7 through 12. The touch sensitive devices disclosed in Ng et al. are generally designed to overlay a computer display and provide positioning information.
The tactile input devices disclosed in the Bobick, Matzke et al. and Ng et al. patents do not satisfy a long-felt need in the art for tactile input devices which accurately and efficiently provide data input for computers and other instrumentation. The devices disclosed in the aforementioned patents fail to satisfy this long-felt need since they effectively only measure position as a fraction of the distance between electrodes located on the boundaries of a sensing region. This leads to measurement inaccuracies since the distance between electrodes is relatively large, thereby causing small errors in the measured fraction to result in large position errors.
Still other tactile sensing devices utilize a grid of electrodes to digitally determine an object's position somewhere on the grid. See U.S. Pat. No. 4,550,221, Mabusth, and U.S. Pat. No. 4,639,720, Rympalski et al. The Mabusth patent discloses a touch sensitive control device which translates touch location to output signals and which includes a substrate that supports first and second interleaved, closely spaced, non-overlapping conducting plates. The plates are aligned in rows and columns so that edges of each plate of an array are proximate to, but spaced apart from, the edges of plates of the other array. The first and second arrays are periodically connected in a multiplexed fashion to a capacitance measuring circuit which measures the change in capacitance in the arrays. In effect, the Mabusth patent discloses a grid of pixels which are capacitively coupled.
Similarly, the Rympalski et al. patent discloses an electronic sketch pad which contains a graphics input pad having an array of transparent capacitive pixels, the capacitance characteristics of which are changed in response to the passing of a conductive tipped stylus over the surface of the pad. The change in capacitance is sensed by buffers disposed along the columns of the pixel matrix as the rows are scanned at a prescribed scanning rate.
Neither the Mabusth patent nor the Rympalski et al. patent satisfy a long-felt need in the art for tactile input devices which exhibit good position resolution of an object. Since the aforementioned patents teach devices which utilize a grid of electrodes and which operate in a "binary" mode, i.e., measure position by examining each electrode and determining that an object is located or is not located at a point on the grid, the resolution of the position measurement is limited to, at best, a few times the grid resolution. This requires an extremely fine pattern of electrodes to achieve acceptable position resolution. However, a fine pattern of electrodes is extremely expensive and, in most cases, not practical. Therefore, the Mabusth and Rympalski et al. patents do not satisfy a long-felt need in the art for tactile sensing devices which can input data to computers or other instruments.